During construction, a blank wall panel is often reserved for subsequent use in the house wiring. Usually, the blank panel should be provided with an opening for use, which is very troublesome. There are also panels with reserved openings in the market, but the size of the opening in these panels is fixed. If there are less wires, the opening would be too large and thus may not provide a good aesthetic look. However, if the wires are more, the size of the opening would not be large enough to hold the wires, which may be very inconvenient. Therefore, a wall panel of incoming and outgoing wires of audio-visual system, in which the size of the opening can be adjusted, is provided.